JPH02247549A - Analysis of multilayered film and formation of multilayered film - Google Patents

Abstract

PURPOSE:To easily make analysis with good productivity without losing the electrolyzing power required for each of respective layers by analyzing the compsn. of the surface layer at the respective timing at the time of film formation to analyze the compsn. modulated structure of the multilayered films formed on a substrate. CONSTITUTION:Fe and Au are subjected to evaporation 12a, 12b in a vacuum chamber 13 and shutters 11a, 11b are opened and closed cooperatively with film thickness sensors 9a, 9b to deposit the Fe and Au by evaporation alternately on the substrate 2 by which the multilayered films are formed. An electron ray is made incident at about 1 deg. glancing angle with the film on the substrate 2 from an electron gun 1 installed in the chamber 13 simultaneously with this film formation to excite a characteristic X-ray. After the characteristic X-ray is detected by a semiconductor detector 13 in the chamber 3 and is amplified 4, the integration coefft. by the characteristic X-ray is separated and is taken into a data processor 6. The outputs of the sensors 9a, 9b are also amplified 10 and are taken into the processor 6 which displays and analyzes the intensity of the characteristic X-ray as the function of a film thickness. The temp. of the substrate 2 is so controlled 7 as to minimize the deviation from the reference value of the characteristic X-ray intensity of the Fe and Au set as the function of the film thickness in the processor 6, by which the multilayered films having the excellent steepness of the boundary are formed.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a method for analyzing a multilayer film and a method for forming the same.
In particular, the present invention relates to a method of analyzing a compositionally modulated structure of a multilayer film formed on a substrate, and a method of forming a multilayer film that controls the compositionally modulated structure based on the analyzed values.

[Prior Art and Problems] Methods for analyzing the compositional modulation structure of a multilayer film formed on a substrate are roughly divided into two types: non-destructive analysis methods and destructive analysis methods. Non-destructive analysis methods include ■X-ray diffraction method (XRD method),
■ Rutherford backscattering method (RBS method) is known as a typical destructive analysis method, ■ Auger spectroscopy (AES method), and cross-sectional thin film transmission electron microscopy (XTEM method) are known as representative methods. However, since all of these analysis methods are carried out after the completion of film formation, there is a problem in that the film formation process cannot be controlled based on these analytical values.

For this reason, as methods that can analyze the multilayer film being formed, (a) high-speed reflection electron diffraction (RHEED) vibration method, and (b) in-situ Auger spectroscopy (in-situ AES method) are used. That is what is being attempted. The features and problems of these methods will be explained below.

(a) RHEED vibration method This method takes advantage of the fact that during epitaxial growth of a single crystal film using a molecular beam epitaxy device, the intensity of the diffracted beam oscillates over time, and the period corresponds to the growth of one atomic layer. This is to monitor the progress of the process and to confirm that the film growth is based on a layered growth mechanism. in this way,
Information regarding the composition modulation structure can be obtained. However, the target is limited to single-crystal films with a specific crystal orientation, and the RHEED vibration phenomenon can only be observed under special film-forming conditions such as an extremely narrow temperature range and film-forming rate. Limited. Furthermore, since physical quantities corresponding to the chemical composition are not directly measured, the information is indirect.

(b) In-situ AES method In this method, in a film forming apparatus such as an MBE apparatus that incorporates an AES apparatus, film forming is interrupted and AES spectroscopic analysis is performed. In the case of in-situ AES measurement, the focal length of the AES spectroscopic analysis tube is as short as approximately 101 m, so it is necessary to install the analysis tube directly above the substrate, which makes it extremely difficult to conduct analysis at the same time as film formation. and is not practical.

Normally, the analysis tube is placed far enough away from the substrate position during film formation in the same vacuum chamber, and installed in a position where the analysis tube will not be contaminated by the film-forming deposition beam and there is no risk that the deposition beam will be blocked by the analysis tube. Alternatively, the substrate is placed in an analysis vacuum chamber provided separately from the film-forming vacuum chamber, and during analysis, vapor deposition is interrupted and the substrate is moved or transported to an analysis tube before analysis is performed. As a result, the time required to interrupt film formation for analysis cannot be ignored during film formation, and if we increase the number of times film formation is interrupted and analyzed in order to obtain sufficient positional resolution, the time required This causes problems that significantly reduce productivity.

On the other hand, as a method for controlling the formation conditions of a multilayer film based on the composition modulation structure in the multilayer film, except for the above-mentioned phase control epitaxy method, all of the methods include the film thickness of each layer, the film formation rate,
This method maintains film formation parameters such as substrate temperature at predetermined values, and does not detect the structure including the laminated interface of the composition modulated film and control film formation based on the result.

Note that the structure of the laminated interface depends on the deposition rate, substrate temperature, surface diffusion coefficient, volume diffusion coefficient, lattice defect density, etc., and these are also factors that depend on the interface structure. Further, in the vapor deposition process, a so-called non-equilibrium or metastable process that proceeds in a supersaturated state is often used.

This is rate-determined by parameters that are difficult to directly control, and therefore it is difficult to obtain the desired laminated interface structure using preset film formation parameters.

Therefore, it is extremely important to control film formation without actually monitoring the film formation process. However, there is no appropriate means to detect the compositionally modulated structure during film formation, or there is no RHEE
It has been difficult to implement this method because it can only be used in special cases, such as the D-vibration method.

The present invention was made in order to solve the above-mentioned conventional problems, and it is possible to easily analyze the compositional modulation structure of a multilayer film formed on a substrate with high productivity without losing the necessary resolution for each layer. The present invention provides a method for forming a multilayer film having a desired composition by controlling film forming conditions based on the analysis value.

[Means for Solving the Problem] The first invention of the present application provides a method for analyzing a multilayer film on a substrate.
An electron beam is incident on the surface of the film being formed so that the oblique angle with respect to the substrate surface is IO'' or less, and the characteristic X-rays excited from the film are directed at an angle of 5 times or less than the critical angle for total reflection of the film. This method of analyzing a multilayer film is characterized in that the compositional modulation structure of the multilayer film is determined by n1 based on the characteristic X-rays.

The second invention of the present application is to heat the substrate while heating the substrate.
When forming a multilayer film by depositing more than one layer, an electron beam is applied to the surface of the film being formed at an oblique angle of I with respect to the substrate surface.
The characteristic X-rays excited from the coating are detected at an angle of five times or less than the critical angle of total reflection of the film, and the composition of the multilayer film is modulated based on the characteristic X-rays. This method of forming a multilayer film is characterized in that the structure is analyzed and the substrate temperature and the evaporation rate of the vapor deposition material are controlled based on the analyzed values.

The third invention of the present application is that when analyzing a multilayer film on a substrate,
X-rays are incident on the surface of the film being formed so that the oblique angle with respect to the substrate surface is less than or equal to 5 times the critical angle of total reflection of the film, and the characteristic X-rays excited from the film are applied to the surface of the film. This method of analyzing a multilayer film is characterized in that detection is performed at an angle that is five times or less than the critical angle of total reflection, and compositional modulation of the multilayer film is measured based on the characteristic X-rays.

The fourth invention of the present application is to heat the substrate while heating the substrate.
When forming a multilayer film by depositing more than one seed, X-rays are applied to the surface of the film being formed at an oblique angle of 10 with respect to the substrate surface.
The characteristic Xi excited from the coating is detected at an angle of five times or less the total reflection critical angle of the coating, and The method for forming a multilayer film is characterized in that the composition modulation structure of the multilayer film is analyzed based on the line, and the substrate temperature and the evaporation rate of the vapor deposition material are controlled based on the analyzed values.

Effect] The reason why it is difficult to analyze a compositionally modulated structure in the conventional method is that the analysis is performed after the film formation is completed. For example, sputter etching required for depth direction analysis using AES requires a technique of sequentially peeling off a film one atomic surface at a time. Even during film formation, controlling the stacking on each negative atomic plane is the so-called ultimate technology, and the difficulty of doing the opposite is understandable.

On the other hand, other non-destructive analysis techniques require difficult techniques to detect the interfacial structure and composition of multilayer films in layers much deeper than the surface layer with atomic-scale resolution. For this reason, the resolution currently achieved in compositional modulation structure analysis is not sufficient.

In the present invention, based on the above considerations, the above technical difficulties can be avoided by analyzing the composition modulated structure during film formation, rather than after the film formation is completed. in this case,
Analysis at each period translates into the problem of analyzing the composition of the surface layer at that time. By continuously performing such analysis operations, analysis values of the compositional modulation structure are obtained as an array of analysis values at each position in the multilayer film. One of the technical problems in this case is that analysis means that can be performed simultaneously with film formation and that has detection sensitivity and resolution at the atomic layer level are required, but the present invention can solve all of these requirements. It is something. Each method of the present invention will be explained below.

In the first invention of the present application, by setting the incident angle of the electron beam to 10" or less and setting the extraction angle for detecting characteristic X-rays to 5 times or less of the critical angle of total reflection of the coating, the following effects can be achieved. One of these is that the electron gun that serves as the electron beam source and the detector that detects characteristic X-rays can be installed at a sufficient distance from the substrate without significantly reducing measurement accuracy or detection sensitivity. Therefore, analysis can be performed simultaneously with film formation without interrupting film formation, and even if film formation is interrupted, analysis can be performed immediately without moving or transporting the substrate.

The other is the detection sensitivity and S/N of the characteristic X-ray that becomes the signal.
This is an improvement in the ratio. That is, the oblique angle of incidence of the electron beam is set to 10''.
By doing the following, the penetration depth of the electron beam can be reduced, the generation area of X-rays is limited to the vicinity of the surface layer, the generation of X-rays is suppressed in areas other than the outermost layer that is the object of measurement, and as a result, noise It is possible to reduce the level. On the other hand, by setting the extraction angle for characteristic X-ray detection to 5 times or less of the critical angle of total reflection of the coating for characteristic X-rays, the path length of characteristic The noise component is reduced due to the increase in mass absorption loss due to the increase in the amount of noise, and the increase in reflection loss at the film interface of the multilayer film, and the signal intensity of the characteristic X-rays excited in the outermost layer is increased due to total reflection from the layers below the outermost layer. do. In this way, due to the strong reflection ability at an angle of less than 5 times the critical angle of total reflection at the film interface of the multilayer film,
Since the S/N ratio of the target characteristic X-ray signal can be increased,
As in the examples described later, sensitivity capable of detecting an increase in film thickness of less than a monoatomic layer can be achieved over a wide range of film thicknesses.

In the invention of Section 2 of the present application, an electron beam is incident on the surface of the film being formed so that the oblique angle with respect to the substrate surface is 10 degrees or less, and the characteristic X-rays excited from the film are reflected at the total reflection critical angle of the film. The composition modulation structure of the multilayer film is analyzed based on the characteristic X-rays, and the substrate temperature and the evaporation rate of the evaporation material are controlled based on the analyzed values, thereby achieving a predetermined composition modulation. A multilayer film having a structure can be formed.

The multilayer film that can be applied to this method is not limited to single crystal, but may be amorphous, and there are almost no limitations on film formation conditions.

In the invention of Section 3 of the present application, X-rays are applied to the surface of the film being formed so that the oblique angle with respect to the substrate surface is 55% of the total reflection critical angle of the film.
The characteristic X-rays excited from the coating are detected at an angle of five times or less than the total reflection critical angle of the coating, and the composition of the multilayer film is modulated based on the characteristic X-rays. By measuring the structure, similar to the invention in Section 1 of the present application described above, it is possible to perform analysis at the same time as film formation without interrupting film formation, and even if film formation is interrupted, operations such as moving and transporting the substrate can be performed. Analysis can be carried out immediately without the need for any additional tests, and the detection sensitivity and S/N ratio of characteristic X-rays can be improved.Furthermore, multilayer films are not deposited in a high vacuum as is the case when electron beams are used. , sputtering, and CVD methods can be applied.Also, unlike the case of electron beams, the generation of continuous spectra that become noise can be almost eliminated.In addition, as an excitation X-ray source for such a method, the most suitable for analysis Although a normal X-ray generator with a wavelength or wavelength range may be used, synchrotron radiation with high X-ray intensity is optimal.

In the invention of Section 4 of the present application, X-rays are incident on the surface of the film being formed such that the oblique angle with respect to the substrate surface is 10" or less than 5 times the critical angle of total reflection of the film, and Excited characteristic X-rays are detected at an angle less than or equal to five times the total reflection critical angle of the coating, the compositional modulation structure of the multilayer film is analyzed based on the characteristic X-rays, and the substrate temperature and By controlling the evaporation rate of the evaporation material, a multilayer film having a predetermined compositional modulation structure can be formed, similar to the invention of Section 2 of the present application described above.

[Example code] Examples of the present invention will be described in detail below.

Example 1 On a substrate, by vacuum evaporation method (Fe25 people/A u2
During film formation to form a multilayer film of 5 people) x 40 layers, the electron beam was applied to the film at an oblique angle of about 1' and an extraction angle of characteristic X-rays from 0" to 4.
Set to a range equivalent to 5 times or less of the total reflection critical angle of 6,
The peak intensity of characteristic X-rays per Fc or Au layer was measured. The relationship between such peak intensity and the film thickness of each layer is shown in FIG.

The results shown in FIG. 1 show that the X-ray intensity per outermost layer is maintained without much attenuation even when the total film thickness increases to about 2,000 layers.

Furthermore, in the case of a single layer film, the X-ray detection sensitivity decreases significantly as the film thickness increases. On the other hand, it was found that when the film thickness is thin, a high detection sensitivity of less than a monoatomic layer can be obtained. In the end, it was experimentally confirmed that in the case of a multilayer film, a detection sensitivity as high as that of a monoatomic layer can be obtained over the entire film thickness.

Example 2 On the substrate, by vacuum evaporation method (Fc25 people/Au2
When forming a multilayer film of 5 layers) x 40 layers, an electron beam is applied to the film at approximately [° The peak intensity of the characteristic X-rays after the Au layer was measured by setting the oblique angle to a range corresponding to 5 times or less of the total reflection critical angle of the characteristic X-ray extraction angle of 0° to 4°. In this case, between 950 and 975 people, F
E was vapor-deposited, and Au was vapor-deposited between the layers of 975 to 1000 layers. FIG. 2 shows the relationship between the thickness of the multilayer film and the characteristic X-ray intensity after 950 people.

In the case of analysis that detects characteristic X-rays, since the effective detection depth is several tens of people, the characteristic X-ray intensity is the integral value of the characteristic X-rays generated within the detection depth range. ing.

Therefore, it is generally necessary to perform deconvolution calculations from measured values expressed as a function of film thickness to back calculate the distribution of characteristic X-ray sources, that is, the composition distribution. However, the measurement results shown in Figure 2 show that the Fe characteristics
The way the line intensity increases and the characteristic X-ray intensity of the Au base layer attenuates is almost the same as when Fe grows in layers on the Au base layer, and each layer grows in layers between these layers. It shows. Therefore, the compositional modulation structure of the 20th layer derived from FIG. 2 is represented by the stepwise distribution shown in FIG. In Figure 3, the resolution of layered growth identification is 2.3.
A corresponding interface layer is set considering it to be an atomic layer. In reality, the structure in this section is unknown.

Example 3 As shown in FIG. 4, Fe and Au were evaporated from electron beam evaporation sources 12a and 12b in a vacuum chamber 13, and
The shutter is operated in conjunction with the film thickness sensors 9as and 9b.

By opening and closing 11b, Fe and AU are alternately deposited on the substrate 2 to form a multilayer film. At the same time as this film formation,
An electron beam is generated from an electron gun l installed in the vacuum chamber 13, and is incident on the film formed on the substrate 2 at an oblique angle of 1@, thereby exciting characteristic X-rays. The generated characteristic X-rays are detected by a semiconductor detector 3 installed in the vacuum chamber 13, and after amplification by an amplifier 4, an integral coefficient due to the characteristic X-rays is separated by a pulse height analyzer 5, and then sent to a data processing device 0. Take in.

At the same time, the outputs of the film thickness sensors 9a and 9b are also amplified by the film thickness controller IO and input into the data processing device 6, where the characteristic X-ray intensity is displayed and analyzed as a function of film thickness. On the other hand, in the data processing device 6, a reference value for the characteristic X-ray intensity of Fe and Au is set in advance as a function of film thickness by a program setting function, and the temperature controller is set so as to minimize the deviation from this reference value. 7 adjusts the output of the substrate heating power source 8, and the substrate heater 14 controls the temperature of the substrate 2. If the substrate temperature is too low, surface diffusion will be suppressed and layered growth will not occur, and if the substrate temperature is too high, volume diffusion will occur, resulting in island-like growth, so layered growth will not occur either. By setting the standard value of characteristic X-ray intensity to correspond to layered growth, an appropriate substrate temperature was maintained, layered growth was promoted, and as a result, a multilayer film with excellent interface steepness was formed.

Embodiment 4 As shown in FIG. 5, the X-rays incident from the continuous X-ray source 21 are monochromated into energy 12 ke/wavelength 1.033 by the monochromator 22, and the slit 23 also serves as a shutter.
It passes through the beryllium window 24 and is guided into the chamber 3B. Inside the chamber 36, the pressure of Ar gas is 5×1
It is maintained at 0-'torr. The incident X-rays are incident on the Sl substrate 25 at an oblique angle of 0.1'. This angle is
The critical angle of total reflection of the X-rays on the Sl substrate 25 is 0.15.
Since the X-rays are smaller than the above, the incident X-rays are totally reflected, and the penetration depth at this time is on the order of several 10 liters.Coating materials are alternately deposited on the Sl substrate 25 from the sputter guns 28a and 26b, and the characteristics generated from the coating are xl is analyzed by an X-ray detector (SSD) 27 at a low extraction angle including the critical angle of total reflection of the characteristic The signals from the thickness detectors 28a and 28b are transmitted to amplifiers 29a and 29.
b, after amplification, it is sent to the personal computer 31, and after arithmetic processing, it is outputted to the printer 34 and floppy disk device 35 as a relationship between characteristic X-ray intensity and film thickness. This output is analyzed after the experiment and converted into a relationship between film thickness and composition, that is, a composition modulation structure. On the other hand, based on the relationship between the characteristic X-ray intensity and the film thickness, the output of the sputter guns 26a and 26b is controlled by the output controller 32 and the sputter gun according to a calculation result programmed in advance so that the characteristic X-ray intensity becomes maximum at the same film thickness. It was controlled via power supplies 33a and 33b. Through such control, we were able to form a multilayer film with excellent interface steepness.

[Effects of the Invention] As detailed above, according to the present invention, there is provided a method for easily analyzing the compositional modulation structure of a multilayer film formed on a substrate without losing the necessary resolution for each layer and with high productivity. It is possible to provide a method in which a multilayer film having a desired composition can be formed by controlling the film forming conditions based on the analysis values.

[Brief explanation of drawings]

FIG. 1 is a characteristic diagram showing the relationship between a single layer film and a multilayer film in Example 1 of the present invention and the peak intensity of characteristic X-rays, and FIGS. 4 and 5 are schematic diagrams showing the multilayer film forming apparatus used in Example 3.4, respectively. ■...Electron gun, 2...Substrate, 3...Semiconductor detector, 6...Data processing device, 7...Temperature controller, 9a
, 9b...film thickness sensor, lla, 1lb-...
Shutter, 12a, 12b - Electron beam evaporation source, 14... Substrate heater, 21... Continuous wavelength X
Radiation source, 25...81 Substrate, 26a, 28b...
Sputter gun, 27...X-ray detector, 28a, 2
8b... Film thickness detector, 31... Personal computer, 32... Output regulator, 33a % 33b...
・Sputter power supply.

Claims (4)

[Claims] (1) When analyzing a multilayer film on a substrate, an electron beam is incident on the surface of the film being formed so that the oblique angle to the substrate surface is 10° or less, and characteristic X-rays excited from the film are collected. Detected at an angle less than or equal to 5 times the total reflection critical angle of the coating,
A method for analyzing a multilayer film, comprising measuring the compositional modulation structure of the multilayer film based on the characteristic X-rays. (2) When forming a multilayer film by depositing two or more types of films on the substrate while heating the substrate, an electron beam is applied to the surface of the film being formed at an oblique angle of 10° with respect to the substrate surface. The characteristic X-rays excited from the coating are detected at an angle of five times or less than the critical angle of total reflection of the coating, and the compositional modulation structure of the multilayer film is analyzed based on the characteristic X-rays. A method for forming a multilayer film, characterized in that the substrate temperature and the evaporation rate of the vapor deposition material are controlled based on the analysis value. (3) When analyzing a multilayer film on a substrate, X-rays are incident on the surface of the film being formed so that the oblique angle with respect to the substrate surface is 5 times or less the critical angle of total reflection of the film. , a multilayer characterized in that characteristic X-rays excited from the coating are detected at an angle that is five times or less than the critical angle of total reflection of the coating, and the compositional modulation structure of the multilayer film is measured based on the characteristic X-rays. Membrane analysis method. (4) When forming a multilayer film by depositing two or more types of films on the substrate while heating the substrate, X-rays are applied to the surface of the film being formed at a viewing angle of 10° with respect to the substrate surface. The characteristic X-rays excited from the coating are detected at an angle of five times or less the total reflection critical angle of the coating, and A method for forming a multilayer film, characterized in that the compositional modulation structure of the multilayer film is analyzed based on the line, and the substrate temperature and the evaporation rate of the vapor deposition material are controlled based on the analyzed values.